RC 2.7 Blender/Volumetric Shading Cycles
Smoke rendering is still not quite possible in 2.7, simply because there is no way to put the smoke voxel data into a cycles shader.

This is a target for 2.71:


  For 2.71, the following features are planned to be worked on:
  
  
  Volume rendering: smoke / voxel textures, better sampling, camera in volume
  


However, it is possible to render volumes based on textures: